Wetlands are an important component of the Andean ecology because of their wealth of biodiversity and endemisms, and the many environmental services they offer. However, baseline knowledge of the types of wetlands and their ecohydrological functioning is currently lacking. Therefore, the objective of this study was to characterize the types and the ecohydrological conditions of wetlands along a precipitation gradient in the Northern Patagonian Andes. This study took advantage of a strong precipitation gradient that occurs due to the rain shadow effect created by the Andes Mountains near the city of San Carlos de Bariloche. We selected five representative wetlands that are at similar elevations and latitudes, but under very different precipitation regimes. At each site, we sampled water and soil chemistry, water levels and floristic composition. We found that hydrological, chemical and vegetation parameters all varied with total precipitation. Sphagnum peatlands occurred in the wettest regions and had year round water saturated soils which formed a peat layer. Meadows were common in the driest regions. We sampled three distinct meadow communities: wet meadows with Juncus balticus, mesic meadows with Festuca pallescens and salt meadows with Distichlis spicata each with a distinct hydrological regime, water chemistry and floristic composition. Marsh/shrub wetlands occurred in the intermediate rainfall areas and had standing water, mineral soils and were vegetated by Nothofagus antarctica and Scirpus spp. Our results indicate the importance of precipitation on wetland structure and function and suggest that any change in precipitation regime will cause significant changes to these ecosystems.

Los humedales representan un componente importante de los ecosistemas andinos debido a su biodiversidad y endemismos, y a los numerosos servicios ambientales que ofrecen. A pesar de esto, el conocimiento básico acerca de los tipos de humedales y su funcionamiento ecohidrológico es escaso. El objetivo de este trabajo fue caracterizar los tipos y condiciones ecohidrólogicas de humedales a lo largo de un gradiente de precipitación en el norte de Patagonia. Aprovechamos el gradiente de precipitación notable que existe como consecuencia de la barrera geográfica de la Cordillera de los Andes en las cercanías de la ciudad de San Carlos de Bariloche. Seleccionamos cinco humedales representativos a una altitud semejante, pero bajo regímenes de precipitación muy diferentes. En cada sitio realizamos análisis químicos de agua y suelo, y registramos los niveles freáticos y la composición florística. Todos los parámetros hidrológicos, químicos y de vegetación variaron con la precipitación. En las zonas más húmedas se encontraron las turberas de Sphagnum que durante todo el año presentaron el suelo saturado con un horizonte de turba. Los mallines se ubicaron en las zonas más secas. Muestreamos tres comunidades diferentes: mallines húmedos con Juncus balticus, mallines mésicos con Festuca pallescens y mallines salinos con Distichlis spicata, cada uno con un régimen hidrológico, química del agua y vegetación diferente. Encontramos pantanos en las zonas intermedias del gradiente, con agua en superficie y suelos minerales, vegetados con Nothofagus antarctica y Scirpus spp. Estos resultados indican la importancia de la precipitación en la estructura de los humedales y sugieren que cualquier modificación de los regímenes pluviométricos podría causar cambios significativos en estos ecosistemas.

A degradação extrínseca de diodos orgânicos emissores de luz (OLEDs) permanece como uma questão crucial, especialmente no que se refere à degradação, devido à exposição à luz. Poucos estudos existem e faltam dados a respeito dos produtos de fotodegradação e respectivos mecanismos, responsáveis pela extinção da luminescência. Com o objetivo de investigar os mecanismos de degradação causados pela exposição à luz de filmes finos de Alq3 usado com sucesso como camada transportadora de elétrons e material emissivo na fabricação de OLEDs, a fotodegradação foi monitorada em função da irradiação com luz UV através das técnicas de fotoabsorção e de fotoemissão nas bordas 1s do carbono, do nitrogênio e do oxigênio bem como nas bordas 2s e 2p do alumínio. A influência da exposição à luz foi simulada com o emprego de três comprimentos de onda diferentes: 254, 365 e 307 nm, os dois primeiros correspondendo aproximadamente a máximos de absorção no espectro de UV do Alq3. Após exposição, todos os espectros apresentam um decréscimo nos sinais de fotoabsorção e de fotoemissão. Entretanto, enquanto a radiação de 307 nm causa mudanças menores nos espectros de NEXAFS, modificações mais acentuadas são observadas para a exposição a 254 e 365 nm. Medidas de fotoemissão para filmes finos de Alq3 não-irradiado e irradiado com luz de 307 nm também foram conduzidas. Embora o sinal correspondente ao alumínio mantém-se praticamente intacto, mudanças mais significativas são observadas nas intensidades e deslocamentos dos picos nas bordas 1s do carbono, do nitrogênio e do oxigênio.

The extrinsic degradation of organic light emitting diodes (OLEDs) remains a critical issue especially concerning degradation due to exposure to light. Very few studies exist and little is known about the related photodegradation products and mechanisms, responsible for quenching of luminescence. In order to gain insight into the degradation mechanisms caused by light exposure of Alq3 thin films, used successfully as electron transport layer and emissive material in the fabrication of OLEDs, we have monitored UV photodegradation through synchrotron radiation-based photoabsorption and photoemission techniques at the carbon, nitrogen, and oxygen 1s edges as well as at the aluminum 2s and 2p edges. The influence of light exposure was simulated using three different wavelengths, namely 254, 365 and 307 nm, the first two nearly corresponding to absorption maxima in the UV spectrum of Alq3. After exposure all spectra show decrease of the photoabsorption and photoemission signals. However, while irradiation at 307 nm causes lesser changes in the total electron yield NEXAFS spectra, strong spectral modifications are observed for 254 and 365 nm exposures. Core level photoemission measurements from non-irradiated and irradiated Alq3 thin films at 307 nm were also performed. While the Al peaks maintained almost intact, changes in peak intensities as well as shifts for carbon, nitrogen and oxygen are much more dramatic.

A fotoluminescência de filmes finos de 1-(3-metilfenil)-1,2,3,4-tetrahidroquinolina-6-carboxialdeído-1,1'-difenilhidrazona foi monitorada em função da irradiação com luz UV. A intensidade da emissão decresce exponencialmente com o tempo de exposição, sugerindo degradação das amostras. Com o objetivo de investigar os mecanismos de degradação e determinar a estrutura eletrônica desse material orgânico usado com sucesso como camada transportadora de buracos na fabricação de diodos orgânicos emissores de luz (OLEDs), foram empregadas as técnicas de fotoabsorção e de fotoemissão nas bordas 1s do carbono e do nitrogênio bem como na banda de valência. A influência da luz solar foi simulada usando radiação síncrotron não-monocromática. Após exposição, todos os espectros apresentam um decréscimo nos sinais de fotoabsorção e de fotoemissão, que é menos acentuado na borda do carbono, apresentando, entretanto, um decréscimo drástico na borda do nitrogênio e na região de valência. O estudo sugere que a perda de nitrogênio é a principal causa para a quebra do sistema π, levando, dessa forma, à falha do dispositivo fabricado com esse composto.

Photoluminescence (PL) emission of 1-(3-methylphenyl)-1,2,3,4-tetrahydroquinoline-6-carboxyaldehyde-1,1 -diphenylhydrazone (MTCD) thin films was monitored as a function of UV irradiation, and it was found to decrease exponentially with the exposure time. In order to gain insight into the degradation mechanisms and evaluate the electronic structure of this organic material used with good results as hole transporting layer (HTL) in the fabrication of organic light emitting diodes (OLEDs), synchrotron radiation-based photoabsorption and photoemission techniques at the carbon and nitrogen 1s edges as well as at the valence band were employed. The influence of sunlight was simulated using non-monochromatized synchrotron radiation. After exposure all the spectra show a decrease of the photoabsorption and photoemission signals, however, while it is less accentuated at the carbon edge, at the nitrogen edge and at the valence region it decreases drastically. The loss of nitrogen is suggested to be the main step in the disruption of the π system, leading to the failure of the devices fabricated with this compound as hole transporting layer.

In this work, a-C:H:Si (DLC-Si) films were produced onto crystalline silicon and polycarbonate substrates by the rf-PACVD technique from gaseous mixtures of CH4 + SiH4 and C2H2 + SiH4. The effects of self-bias and gas composition upon mechanical and optical properties of the films were investigated. Micro-hardness, residual stress, surface roughness and refractive index measurements were employed for characterization. By incorporating low concentrations of silicon and by exploring the more favorable conditions for the rf-PACVD deposition technique, highly adherent DLC-Si thin films were produced with reduced internal stresses (lower than 1 GPa), high hardness (around 20 GPa) and high deposition rates (up to 10 µm/h). Results that show the technological viability of this material for application as protective coatings for polycarbonates are also discussed.

In this work the growth and the characterization of red emitting triple-layer electroluminescent organic devices using vacuum deposited (Eu(TTA)3(TPPO)2) europium complex as emitting layer are described. The observed electroluminescence (EL) is characteristic of the Eu3+ emission. In this device the hole transport layer is obtained using a thin film of 1-(3-methylphenyl)- 1,2,3,4 tetrahydroquinoline-6-carboxyaldehyde-1,1'-diphenylhydrazone (MTCD), while the tris(8- hydroxyquinoline aluminum) (Alq3) is used as electron transport layer (ETL).